1. Field of the Invention
The present invention relates to an illumination device for a microscope, in particular to an incident illumination device for a stereomicroscope, utilizing several point light sources, such as a light-emitting diode, arranged on a carrier element; and to a microscope having such an illumination device.
2. Description of Related Art
DE 10 2005 036 230 B3 discloses a stereomicroscope system having an incident illumination device, the stereomicroscope system comprising a vertical focusing column on which a focusing arm is mounted in vertically displaceable fashion. The focusing arm extends in arc-shaped fashion away from the focusing column, and terminates in an opening that serves to receive the actual stereomicroscope. Several light-emitting diodes are fixedly arranged on the focusing arm, on the one hand around the receiving opening for the stereomicroscope and on the other hand along the arc-shaped portion of the focusing arm. High-performance white-light diodes are used as light-emitting diodes. The light-emitting diodes can be operated individually or in groups, the brightness also being controllable individually or in groups. The light-emitting diodes arranged around the receiving opening serve for vertical/top down incident illumination, while the light-emitting diodes arranged along the arc-shaped portion of the focusing column make available an oblique illumination (angle range from 15 to 105 degrees).
In the context of the aforesaid document, the light-emitting diodes are arranged fixedly on the focusing arm. The elevation angle (height from which the illumination occurs) is therefore predefined by the arrangement of the light-emitting diodes for a fixed azimuth angle. The same applies to the azimuth angle (i.e. the angle on the horizontal circle on which the light-emitting diodes are located around the receiving opening) for which the elevation angle is predefined. Flexible illumination from different azimuth and elevation angles is therefore not possible. A further disadvantage of the proposed arrangement is that the high-performance diodes generate considerable heat, which is conveyed to the focusing arm that in turn is joined to the focusing column.
European Patent EP 1 150 154 B1 discloses an arrangement for (incident) illumination in microscopes having an annular carrier oriented around the optical axis, the illuminating means (white-light diodes) being arranged in the annular carrier in several concentric annular rows located in one plane. The plane of the annular carrier is perpendicular to the optical axis. The light-emitting diodes possess a relatively small emission angle and are directed toward the optical axis of the microscope. The light-emitting diodes can likewise be interconnected in groups, and are operated via a controllable constant-current source.
Here as well, a disadvantage of this proposed illumination arrangement is that azimuthal direction of the illumination to the specimen can be accomplished only by applying control to individual illumination means. Because the latter are arranged at a short distance from one another because of the illumination homogeneity that must be achieved, the number of illumination means to be provided increases greatly with the number of desired angles.
Additionally known, from U.S. Pat. No. 5,038,258, is an illumination arrangement that comprises a semi-spherical carrier at whose center point the object plane of the microscope is placed. Point light sources such as light-emitting diodes are arranged in circular fashion on the carrier at different heights, i.e. planes above the object plane. Here as well, the number and manner of arrangement of the light-emitting diodes therefore determine the possible elevation and azimuth angles at which specimen illumination is possible. The brightness values of the light-emitting diodes can be individually controlled for this purpose. Here as well, an illumination that is flexible in terms of angle requires a large number of illuminating means. The dome-shaped arrangement of the light-emitting diodes on concentric annular rings furthermore impedes access to the specimen.
AT 136 806 B discloses an illuminating device the illuminating device comprising a carriage for receiving one or more miniature incandescent lamps as a light source, and a holder attachable to the microscope tube, the carriage together with the holder being displaceable about the tube axis, in a horizontal plane, on an intermediate piece having a circular guide. Microscope-referred illumination of the focal plane that is defined by the objective being used can thereby be achieved. Because the aforesaid intermediate piece, and the arc-shaped holder, attached thereto, for the carriage having the light source, are fixed in terms of their geometry, it is not apparent how, in the context of an objective change, the illumination device can be adapted to the new objective. The illumination device proposed therein is not suitable for the use of a microscope having an objective turret, as is usual at present. Attachment of the illumination device to the microscope tube furthermore results in the previously mentioned disadvantageous heat transfer to the microscope optics.
DE 195 41 420 A1 discloses a stereomicroscope arrangement having a main observer's microscope and an assistant observer's microscope, and an illumination unit that directs light toward the object plane through the objective that is common to the main and assistant observers' microscopes. The illumination unit is attached to the microscope and can be brought, by rotation about the optical axis, into a position that is optimal for the particular observer. The setting of different elevation and azimuth angles is not addressed in this document.
U.S. Pat. No. 5,570,228 discloses a transmitted illumination device having two or more frames each having a light source, the light of which is directed via a light guide toward the object plane. A suspension point of the light guide can be shifted along a circular-arc-shaped guide. The elevation angle can be modified by means of this adjustment.
DE 10 2005 034 829 A1 discloses a microscope having a surgical slit lamp with a laser light source, the illumination apparatus being mounted displaceably along a circular-arc-segment carrier, the displacement occurring in a plane perpendicular to the object plane. The circular-arc-segment carrier is arranged on the back side of the microscope housing.
Lastly, the use of external illuminating means is known in principle. The illuminating means is placed on a separate stand next to the microscope, and is directed at an arbitrary angle onto the specimen. If the angle between the object plane and illumination axis is approximately 90 degrees, this is referred to generally as vertical illumination, which is used to observe depressions in specimens. At flatter illumination angles an oblique illumination is obtained, which serves to detect three-dimensional specimen structures. At very flat illumination angles, i.e. raking/grazing illumination (almost parallel to the object plane), the term “dark-field illumination” is used. This allows relief and other surface structures to be detected, light scattered and reflected from the structures being used for detection. Separate placement of an illuminating means on a stand next to the microscope costs additional space, represents a potential hazard, and can interfere with work on the specimen. To change the azimuth or elevation angle, the stand must be repositioned and the lighting means must be redirected onto the specimen. This makes it difficult to return to a setting once it has been arrived at.